1. Field of the Invention
This invention generally relates to an optical pick-up for use in an optical information recording and reproducing system, and, in particular, to a multi-beam optical pick-up using a multiple of beams for use in an optical disc system.
2. Description of the Prior Art
A multiple beam optical disc system in which a pair of light beams is focused onto a recording surface of an optical disc to form a pair of light spots located adjacent to each other so as to carry out a confirmed recording operation, i.e., recording followed by reproduction of recorded information for confirmation, and a multiple recording operation is well known. A multi-beam optical system for use in such a multi-beam optical disc system is described, for example, in Japanese Patent Post-examination Pub. No. 57-60697, Japanese Patent Laid-open Pub. Nos. 62-119744 and 62-119745 and Japanese Utility Model Laid-open Pub. Nos. 63-11726 and 63-11727. A multi-beam optical pick-up is also described in Japanese Patent Application No. 62-298652, which has been assigned to the assignee of this application and thus is hereby incorporated by reference, and from which a U.S. patent application Ser. No. 276,681 was filed on Nov. 28, 1988 claiming Priority.
In such a multi-beam optical pick-up, if two light beams are emitted from a light source, a first light beam is used for recording information and the remaining second light beam is used for reproducing the information just recorded by the first light beam for the purpose of confirmation. Thus, as compared with an optical pick-up using a single light beam, in accordance with such a multi-beam optical pick-up, recording and reproduction for confirmation can be carried out almost at the same time. Besides, since two or more light beams are used, a multiple recording or reproducing operation can be carried out.
However, in such a multi-beam optical pick-up, it is required to position two light beams properly at a desired recording track on the recording surface of an optical disc and, for this purpose, it is preferable to detect a tracking error for each of the light beams which impinges on the optical disc. Although various multi-beam optical pick-ups are proposed as noted above, none of them teaches providing a tracking servo control for each of the light beams used.